[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Water hardness - precision
"Roger S. Miller" writes:
(snip)
>
> From a slightly more technical standpoint, the degree scales > represent the built-in precision of the test kits. I think getting > results in small whole numbers discourages people from speculating > about fractional parts in between. Results in larger numbers lets > people think that maybe there is something between 18 ppm and 35 ppm > (1 degree and 2 degrees) that they can read from their test kits, > when in fact the precision of the kit isn't good enough to allow > that.
Hi Roger,
You are right that many (most?) test kits do no do too well in the
precision department. That's unfortunate, but often cannot be helped!
You are also probably right on the psychology of compulsive "value
splitters", who use a carving knife and expect scalpel precision.
Current test kits for measuring water hardness are precise enough not to
leave too much "space" to be subdivided in an attempt to increase
precision. (Funny, how everybody seems to desire *precision* and NOT
*accuracy*!) Your example of 18 vs. 35 ppm is valid when you convert
"degrees" to ppm (assuming you obtained your "degree" results in whole
numbers).
My LaMotte total hardness kit (model AG-25) is calibrated in 4 ppm
divisions and without too much imagination can be read to 2 ppm. That
should be precise enough and satisfy most "value splitters"!
I think, that the question "why doesn't the industry switch to ppm" can
best be answered that here we have a "chicken and egg" situation:
One one hand the commercial hobby literature is quite sloppy in matters
of science. The editors are probably not even aware that something is
amiss - they rely on translators who know about fish as the low
cholesterol meat you buy in the supermarket. They use "degrees", because
it was used in the original, usually German, text they are translating -
and they do not know any different.
On the other hand we have the suppliers of test kits. They tune their
product to the perceived demand of the market. Many (most?) kits show
you how to calculate the results either way. From that point on it is up
to the user, who is confused by the books....
On the "third hand" the water softener industry likes the mumbo-jumbo of
"points", I think not so much to confuse the prospective customers, but
because people are used to the term "points" (as in a mortgage) but
can't even pronounce easily "parts-per-million"!
And, on the "fourth hand" comes your idea (I think that it has validity)
that people are precision hounds and "feel better" with their choices
limited to whole numbers.
Also, because nobody (except a FEW fish-keepers) has a vested interest
to change the present conditions, nothing is being (or will be) done.
But now I am not even certain about the fish-keepers: In response to the
post on hardness I received a nice letter that, among other things,
informed me that "for the sake of simplicity" the AGA policy defines
"alkalinity" as "carbonate hardness"!
So, how can things change for the better, if erroneous information is
codified by one part of the hobby?
Best,
George